I don't think you lost your other Phals from root rot. The roots were dried up so either over or under watering (I would guess overwatering as that's the most common Phal watering problem) but hard to tell without being there. Your other plant with the dead roots actually looked really good and I think, except for watering issues, you were doing well.
Phalaenopsis need bright but indirect light - a bright window works perfectly. Their leaves are bright green when happy. (But leaf color also has to do with flower color - lighter flowers, lighter leaves. Darker flowers, darker leaves) I grow Phals under lights but also in a north facing window sill without lights. Lights are an investment because they aren't all created equally. My lights are LEDs and give off 8000 to 9000 lux (you can put an app on your phone to measure light). Mine bloom every year at that light level but the American Orchid Society recommends 10,000 to 15,000 lux.
But, as I've stated before, it might be water quality that is killing your plants. Try some distilled or RO water and see if there are improvements in plant health. Bad water will kill them faster than incorrect light and light does not affect roots.
